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Diamond Lake bubbles boggle minds of scientists

Specialist thinks the gas may be relevant to the lake's ongoing summer water-quality problems

Sets of disappearing bubbles discovered last summer deep beneath Diamond Lake have scientists baffled over what they are, why they're there and where they went.

The bubbles appeared last August during a special mapping on the lake bottom, when sonar equipment first mistook the ascending bubbles as fish that rose then disappeared before reaching the surface.

More sophisticated equipment identified them as gas bubbles, and the bubbles were discovered in concentrated patches that formed a near-straight line north to south along the lake's eastern side.

When the scientists went back to the eastern Douglas County lake in November to capture and analyze these bubbles, they were gone. And they haven't been seen since.

Possible explanations range from volcanic gases to groundwater to decomposing organic matter, but none quite fit the come-and-go scenario of the bubbles, researchers said.

There were bubbles, and then there were no bubbles, said Dave Loomis, a biologist with the Oregon Department of Fish and Wildlife. But what they are and what they mean? We don't know.

But it's weird, like we have 'Bizarro Lake,' Loomis said.

A Bend lake specialist hopes to crack the mystery because it may be relevant to the lake's ongoing summer water-quality problems associated with the explosion of illegally introduced tui chubs.

For the past two summers, vast mats of toxic blue-green algae called anabaena have blossomed there, even triggering a three-week ban on swimming and wading until the algae died off.

The bubbles may play some role in that algae growth because they carry nutrients from the lake bottom toward the surface, helping feed the algae, said Joe Eilers, the Bend specialist who discovered the bubbles.

It's highly relevant and it's important we follow up on all significant leads, Eilers said. We view this as a piece of information we didn't have before.

And it's fascinating.

The bubble phenomenon is outlined in a yet-to-be-released report by Eilers on water quality and fishery problems at the troubled lake atop the Cascades. The report is expected to be released this week through the ODFW, Eilers said.

The agency now is looking for money to re-hire Eilers to find, collect and analyze the bubbles this spring ' if they come back.

In reams of various studies of the often crystal-clear lake, none have unearthed the bubbles ' not even an intensive 1970s study by the federal Environmental Protection Agency probing the nutrient levels in the lake, Eilers said.

One possible explanation is that the bubbles are caused when super-saturated groundwater discharges carbon monoxide as it seeps into the lake, Eilers said. That would explain why the pockets seemed to form a line, as if they were seeping through a lateral crack in the bedrock, he said.

But Eilers said surging groundwater like that doesn't usually stop altogether in less than three months.

Gases released from decomposing organic matter are unlikely because the bubbles occurred in spots where the lake bottom was firmer and the organic matter levels were relatively low, Eilers said.

Bubbles caused by the release of volcanic gas are present in nearby East Lake, and Diamond Lake is ringed by mountains created by volcanic activity. But the most common volcanic gas is hydrogen sulfide that sports a rotten-egg scent ' and no such smell was found at Diamond Lake, Eilers said.

Other possible gases could be methane released from decomposing matter or volcanic gases, or even argon that could stem from volcanic spurts, he said.

It's very likely that small tectonic movements cause the gases to turn on and off, he said.

There is some indication that those gases may be back on.

In January, Eilers flew over Diamond Lake as part of his mapping work, and photographs showed weak spots in the ice that covers the lake, he said. Those weak spots coincided with the bubble areas, he said.

It's all really interesting, said Loomis, the ODFW's Umpqua watershed manager. But all we have now is that there's bubbles at the bottom of the lake.

Reach reporter Mark Freeman at 776-4470, or e-mail